Return a list rather than dict_values in XmlManifest.projects()

dict.values() produce dict_values objects rather than list objects.
Convert this to a list to maintain functionality with certain functions.

Change-Id: Ie76269e19f8d68479a1d7ae03aa965252d759a9e

manifest_xml.py

@@ -310,7 +310,7 @@ class XmlManifest(object):
   @property
   def projects(self):
     self._Load()
-    return self._paths.values()
+    return list(self._paths.values())
 
   @property
   def remotes(self):